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I right-clicked a POST request in Chrome and selected "Copy as cURL".

I got a curl command that includes the following:

--data-binary $'------WebKitFormBound

I am used to seeing curl requests that have a single flag and string. Like this:

$ curl -0 "output.txt"

I understand that the --data-binary command will POST binary data (presumably after converting the string, after the --data-binary switch, into binary). But what does the dollar sign mean?

What does the curl request mean if it has two dashes and a dollar sign?

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2 Answers 2

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The notation being used there $'...' is a special form of quoting a string recognised by a few shells like ksh (where it originated), zsh and bash.

excerpt

Strings that are scanned for ANSI C like escape sequences. The Syntax is $'string'

Example

$ echo $'hola\n'
hola

$

References

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2
  • 1
    so basically the command says "scan the string for escape characters and print the formatted string then convert that printed string to binary"
    – bernie2436
    Commented Feb 17, 2014 at 20:55
  • @akh2103 - yes I believe that's how it works.
    – slm ♦
    Commented Feb 17, 2014 at 20:56
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Part of your question was answered. In answer to the other part, the "two dashes" is typically the long form use of a parameter.

It is common for commands to have both a long and a short form for any given parameter. For example, if you look at the manual for curl, you will see:

-a, --append
    (FTP  SFTP)  When  used  in  an  upload,  this makes curl...

The -a, --append means that you can use either -a or --append in order to use that parameter. The -a could be considered an abbreviation. Whether you use one or the other makes no difference, it is personal preference.

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